DESCRIPTION: (Adapted from the Applicant's Abstract.) The overall objective of the proposed research is to investigate central nervous system adaptation in the vestibulo-ocular reflex (VOR). Adaptive changes in VOR gain occur when mismatch of the visual and the vestibular signals causes images to slip on the retina during head movements. It is the purpose of this proposal to investigate anatomical and pharmacological substrates of adaptive VOR gain changes. The overall objective of the proposed research is to test if the anatomical loci and neurochemical mechanisms are the same or different for short and long term adaptation of the VOR. Since the applicant's previous studies in the goldfish have shown that there is a recovery of adaptive function after cerebellectomy, he will examine whether similar mechanisms underlie the VOR adaptive gain changes that take place after long term chronic cerebellectomy. To explore the pharmacology of the system, he will apply compounds related to noradrenergic and excitatory amino acid function. These compounds will be applied diffusely and then locally within discrete regions of the brain. These compounds, which include agonists and antagonists of norepinepherine, NMDA and quisqualate, are thought to have an influence on neuroplastic changes in a number of different structures and systems in the central nervous system. An additional dimension of the study is the use of temperature changes as a means of dissecting out baseline and adaptively altered components of the VOR. Since a decrease in temperature has been shown to inactivate reversibly a recently modified VOR, the investigator will use temperature as an independent variable to test for similarities or differences in the mechanisms responsible for VOR adaptation under the various conditions.